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104                       SECULAR  INCREASE   IN  SIZE                  CHAP, iv
have left a dwarfish offspring; that there were giants of
old, and that there is a puny race to-day. As a matter of
ffxct, the study of the gradual evolution of the early Tertiary
Mammalia Into their descendants of later times shows very
plainly the truth of this interesting generalisation: That the
primitive types were all small creatures, and that in those
instances where we can trace a pedigree, there was a gradual
increase in size up to a point where greater increase led to
extinction. We point out later on a number of facts illus-
trating this matter in detail. It has been ascertained, for
instance, that the pedigree of the Horses, the Camels, the Ehino-
ceroses, and many other groups, commences with small forms
and culminates in large ones. It may be urged that such
animals as the Tapir are to-day smallish forms, and that related
to them in the past were the gigantic Titanotheres; but in this
and similar cases it will be found that the extinct giants were
not in the direct line of pedigree, but represented side-branches
which waxed huge on their own account and then disappeared.